1. The Field of the Invention
The present invention relates systems and methods for measuring and weighing a moving mass. More particularly, the present invention relates to measuring and weighing a mass that is on a moving and/or sloped platform and subject to external forces other than the gravitational force.
2. The Prior State of the Art
A primary business goal is to maximize output or production while minimizing costs. With regard to agricultural operations maximizing output potentially includes measuring the weight or volume of a crop, collecting weight data while harvesting the crop to develop a crop yield map, and using the crop yield map to identify problem areas of an agricultural field. Maximizing output also includes ensuring that the vehicles used to transport a harvested crop to a destination are fully loaded but not overloaded. In many harvest scenarios, trucks are loaded as the crop is being harvested and an overloaded truck not only may damage the truck but may also incur overload penalties. In the alternative, a less than fully loaded truck is inefficient because more loads are needed to transport the crop to market.
The act of weighing the crop as it is harvested has presented many challenges which are related to the manner in which crops are harvested. For example, many agricultural vehicles such as harvesters use conveyors to transport a crop from the harvesting vehicle to a transport truck. Many different types of conveyors have been developed including augers and continuous belt or chain link devices, and while conveyors provide an effective method for loading crops onto trucks, they present various problems when the weight of the crop being harvested is measured.
It is inconvenient and inefficient for a conveyor to deposit the crops onto a static scale before loading the crops in a truck, because the crop must then be removed from the scale and because additional time and equipment are required to harvest the crop. Another approach for weighing a crop involves positioning the entire conveyor assembly on a scale platform and subtracting the weight of an empty conveyor from the measured weight of the crop and the conveyor. In any case, weighing accuracy is compromised due to the slope and motion of the machine.
Another method for determining the weight of a crop while it is being harvested is to monitor the power required by a conveyor to transport the crop from the harvester to a truck. These systems have proved problematic, especially on variable pitch conveyors. The power consumption of a conveyor assembly does not uniquely correspond to the weight of the material due to the variable friction forces of the system. Thus, it has proven difficult to accurately measure the weight of material carried on a conveyor using this method.
Weighing crops as they are being harvested or weighing other materials that are carried by moving vehicles has been difficult, due to dynamic forces (i.e. acceleration) and the variable slope of the vehicles. For example, a harvester that traverses a field is subjected to dynamic forces and has a variable angular position with respect to the horizontal plane as it encounters and moves over uneven terrain. Weighing harvested crops using a simple load cell under these conditions leads to inaccurate results due to both the dynamic forces associated with movement and the variable angle of the load cell. These problems associated with weighing material have also been experienced in other agricultural and industrial settings. For example, accurate measurements of animal feed, gravel cement, and other bulk materials on moving platforms have been difficult to obtain.
In view of the foregoing, there is a need in the art for weighing systems that are capable of accurately measuring materials, such as crops, as the material is carried on a vehicle that is subjected to dynamic forces and variable inclination. It would also be desirable for such weighing systems to be capable of use with a variety of materials environments, and vehicles.